Working with groups in LDAP can be a tricky business, mostly because there are
so many different kinds. This module includes an extensible API for working with
any kind of group and includes implementations for the most common ones.
LDAPGroupType is a base class whose concrete
subclasses can determine group membership for particular grouping mechanisms.
Four built-in subclasses cover most grouping mechanisms:

posixGroup and nisNetgroup objects are somewhat specialized, so they get their
own classes. The other two cover mechanisms whereby a group object stores a list
of its members as distinguished names. This includes groupOfNames,
groupOfUniqueNames, and Active Directory groups, among others. The nested
variant allows groups to contain other groups, to as many levels as you like.
For convenience and readability, several trivial subclasses of the above are
provided:

To get started, you’ll need to provide some basic information about your LDAP
groups. AUTH_LDAP_GROUP_SEARCH is an
LDAPSearch object that identifies the set of
relevant group objects. That is, all groups that users might belong to as well
as any others that we might need to know about (in the case of nested groups,
for example). AUTH_LDAP_GROUP_TYPE is an instance of the class
corresponding to the type of group that will be returned by
AUTH_LDAP_GROUP_SEARCH. All groups referenced elsewhere in the
configuration must be of this type and part of the search results.

The simplest use of groups is to limit the users who are allowed to log in. If
AUTH_LDAP_REQUIRE_GROUP is set, then only users who are members of
that group will successfully authenticate. AUTH_LDAP_DENY_GROUP is
the reverse: if given, members of this group will be rejected.

It is important to note a couple features of the example above. First and foremost,
this handles the case of both AUTH_LDAP_REQUIRE_GROUP and AUTH_LDAP_DENY_GROUP
in one setting. Second, you can use three operators on these queries: &, |,
and ~: and, or, and not, respectively.

When groups are configured, you can always get the list of a user’s groups from
user.ldap_user.group_dns or user.ldap_user.group_names. More advanced
uses of groups are covered in the next two sections.